- Jackalope (American) – Rabbit with antlers
- Jack Frost - Personified of ice, winter and snow
- Jack-In-Irons (English) – Malevolent giant
- Jack-o'-lantern (Medieval folklore) – Vegetal lantern
- Jaculus (Medieval Bestiaries) – Winged serpent or small dragon
- Jasconius (Medieval folklore) – Island-sized fish
- Jasy Jaterei (Guaraní) – Nature guardian and bogeyman
- Jatayu (Hindu mythology) – Vulture demigod
- Jaud (Slavic) – Vampirised premature baby
- Jenglot (Java) – Vampiric little people
- Jengu (Sawa) – Water spirit
- Jentil (Basque) – Megalith-building giant
- Jenu (Mi'kmaq) – Anthropophagous giant
- Jerff (Swedish) – Gluttonous dog-cat-fox hybrid
- Jersey Devil (American) – Demonic dragon or flying demon who was given birth to by an American living in New Jersey
- Jian (Chinese) – One-eyed, one-winged bird who requires a mate for survival
- Jiangshi (Chinese) – Life-draining, reanimated corpse
- Jiaolong (Chinese) – Dragon
- Jibakurei (Japanese) – Spirit that protects a specific place
- Jievaras (Lithuanian) – House spirit
- Jikininki (Japanese) – Corpse-eating ghost
- Jinn (Arabian, Islamic) – Spiritual creatures; genii
- Jipijka'm (Mi'kmaq) – Underwater horned snake; lives in lakes and eats humans
- Jiufeng (Chinese) – Nine-headed bird worshiped by ancient natives in Hubei Province.
- Jiu tou niao (Chinese) – Nine-headed, demonic bird
- Jogah (Iroquois) – Little people nature spirit
- Jörmungandr (Norse) – Sea serpent
- Jorōgumo (Japanese) – Spider woman
- Jotai (Japanese) – Animated folding screen cloth
- Jötunn (Norse) – Gigantic nature spirits
- Jujak (Korean) – Bird
- Jumbee (Guyanese) – Malevolent spirit